Polysiloxane with cycloalkyl modifier composition and biomedical devices

ABSTRACT

Monomeric polysiloxanes endcapped with activated unsaturated groups are copolymerized with cycloalkyl modulus modifiers and tear film stabilizers to form hard, gas permeable, polysiloxane contact lenses and other biomedical devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to hard, gas permeable, biomedical devicesincluding contact lenses prepared from monomeric polysiloxanespolymerized with a cycloalkyl modulus modifier and a tear filmstabilizer.

2. Prior Art Statement

U.S. Pat. No. 3,639,362 discloses optical lenses with high glasstransition points made from copolymers of (a) adamantane acrylate ormethacrylate and (b) a second polymerizable, unsaturated monomer such asmethylmethacrylate, styrene, acrylonitrile or vinyl chloride.

U.S. Pat. No. 3,808,178 discloses contact lenses fabricated from acopolymer of a polysiloxanylalkyl acrylic ester and an alkyl acrylicester. The copolymer is said to have increased oxygen permeability.Wettability can be imparted to the copolymer by the addition of about0.1 to about 10 percent by weight of the one or more hydrophilicmonomers such as hydroxyalkyl acrylates and methacrylates, acrylic andmethacrylic acid, acrylamide, glycidyl acrylate and N-vinylpyrrolidinone.

U.S. Pat. No. 4,152,508 discloses hard contact lenses having a highoxygen permeability. The lens material is a copolymer of asiloxanylalkyl ester monomer, and itaconate ester and an ester ofacrylic or methacrylic acid. Representatives of itaconate esters includephenyl itaconate, diphenyl itaconate and methyl phenyl itaconate.

U.S. Pat. No. 4,153,641 discloses contact lenses made from polymers andcopolymers comprising poly(organosiloxane) polymers and copolymersformed by polymerizing a poly(organosiloxane) monomer α,ω terminallybonded through divalent hydrocarbon groups to polymerized, free radicalpolymerizably activated, unsaturated groups forming a polymer in acrosslinked network. Additionally, specific comonomers are disclosedwhich include lower esters of acrylic and methacrylic acid, styryls andN-vinyl pyrrolidinone which may be copolymerized with the abovedescribed poly(organosiloxane) to form a copolymer. The instantinvention preferred polysiloxane monomers include the samepoly(organosiloxane) monomers described above.

U.S. Pat. No. 4,208,506 discloses soft contact lenses made from polymersand copolymers comprising polyparaffinsiloxane polymers and copolymersformed by polymerizing a polyparaffinsiloxane monomer α,ω terminallybonded through divalent hydrocarbon groups to polymerized, free radicalpolymerizably activated, unsaturated groups forming a polymer in acrosslinked network. Additionally, specific comonomers are disclosedwhich include lower esters of acrylic and methacrylic acid, styryls andN-vinyl pyrrolidinone which may be copolymerized with the abovedescribed polyparaffinsiloxane monomer to form a copolymer. The instantinvention preferred polysiloxane monomers include the samepolyparaffinsiloxane monomers described above.

U.S. Pat. No. 4,228,269 discloses contact lenses and blanks for same aremade by polymerizing at least one styrene type monomer, optionally withat least one crosslinking monomer and optionally with othermonoolefinically unsaturated monomers. Preferably the styrene monomer isa styrene substituted in the ring by at least one alkyl group, e.g.,tertiary-butyl styrene and/or isopropyl styrene. The lenses have high aspermeability.

U.S. Pat. No. 4,254,248, granted on application Ser. No. 074,922 by GaryD. Friends et al., discloses monomeric polysiloxanes endcapped withactivated unsaturated groups polymerized with a comonomer comprising apolycyclic ester of acrylic acid or methacrylic acid to form a softcontact lens. Though not a polycyclic, menthyl acrylate (andmethacrylate) is disclosed as being within the scope of the disclosure.The polycyclic monomer is present in an amount from about 20 to 80weight percent of the total polymer. These instant polysiloxanecopolymer soft contact lenses have unexpectedly high tear strengths andunexpectedly high modulus of elasticity.

U.S. Pat. No. 4,276,402, granted on application Ser. No. 075,365 byRichard E. Chromecek et al., discloses monomeric polysiloxanes endcappedwith activated unsaturated groups polymerized with acrylic acid andpolycyclic ester of acrylic acid or methacrylic acid to form a softcontact lens. The polycyclic monomer is present in an amount from about5 to 50 weight percent of the total polymer and the acrylic acid ispresent in an amount from 1 to about 30 weight percent. These terpolymersoft contact lenses have unexpectedly high tensile strengths andimproved tear strengths as compared to copolymers of polysiloxane andacrylic acid.

U.K. patent application No. 2,036,765 discloses soft contact lensescomprised of a hydrated copolymer of a major proportion of anhydroxyalkyl acrylate or methacrylate, up to 12% by weight of anyethylenically unsaturated acid or anhydride, a major proportion of acrosslinking monomer and a minor proportion of styrene or substitutedstyrene, the free acid or anhydride groups being in bulk form. Thereinforcing effect of the styrene in the copolymer can be increased byincorporating it in more concentrated sequence, e.g., as a blockcopolymer.

SUMMARY OF THE INVENTION

In accordance with this invention, biomedical devices, including opticalcontact lenses, are provided which are made from three-dimensionalnetwork polymerizates of (1) polysiloxanes α,ω terminally bonded througha divalent hydrocarbon group to an activated, unsaturated group, (2) acycloalkyl modulus modifier and (3) a tear film stabilizer.

The present invention provides materials which can be usefully employedfor the fabrication of prostheses such as heart valves and intraocularlenses, optical contact lenses or films. More particularly, the instantinvention concerns hard contact lenses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The monomers employed in accordance with this invention are readilypolymerized to form three-dimensional polymeric networks which permitthe transport of oxygen and are optically clear, strong and hard.

The preferred polysiloxanes employed are (I) poly(organosiloxanes) ofthe formula ##STR1## or (II) polyparaffinsiloxanes of the formula##STR2## wherein A is an activated unsaturated group; R is a divalenthydrocarbon radical having from 1 to about 22 carbon atoms, R¹, R², R₃and R⁴ are each independently selected from the group consisting of amonovalent hydrocarbon radical having from 1 to about 21 carbon atomsand a halogen substituted monovalent hydrocarbon radical having from 1to about 12 carbon atoms; R⁵ and R⁶ can be the same or different and areselected from the group consisting of hydrogen, a hydrocarbon radicalcontaining from 1 to about 12 carbon atoms, a carboxylic acid group, acarboxylic acid ester group represented by the formula --C(O)OR⁷ whereinR⁷ is selected from the group consisting of a hydrocarbon groupcontaining from 1 to about 12 carbon atoms and a carboxylic acid amiderepresented by the formula --C(O)NR⁸ R⁹ wherein R⁸ and R⁹ can be thesame or different and each is selected from the group consisting ofhydrogen and a hydrocarbon group containing from 1 to about 12 carbonatoms; x is from 2 to 25, m is an integer from 0 to 100 and n is aninteger from 1 to 100. Desirably m will be from 0 to 50. More preferablym will be from 0 to 25. Desirably n will be from 1 to 50 and morepreferably from 1 to 25. Desirably x will be from 2 to 10 and morepreferably is 2 or 3.

The term "an activated unsaturated group" refers to a group which has asubstituent which functions through resonance to increase the freeradical stability or activity of the double bond, thereby facilitatingfree radical polymerization of the monomer. These activated unsaturatedgroups will polymerize to form a polymer with a crosslinkedthree-dimensional network. Preferably the activating groups present aresuch that the monomers lend themselves to polymerization under mildconditions, such as ambient temperatures. Preferred activating groupsinclude:

    ______________________________________                                        2-cyanoacryloxy     CH.sub.2 :C(C:N)C(O)O                                     acrylonitryl        CH.sub.2 :C(C:N)                                          acrylamido          CH.sub.2 :CHC(O)NH                                        acryloxy            CH.sub.2 :CHC(O)O                                         methacryloxy        CH.sub.2 :C(CH.sub.3)C(O)O                                styryl              CH.sub.2 :CHC.sub.6 H.sub.4                               N-vinyl-2-pyrrolidinone-x-yl wherein                                          x may be 3, 4 or 5                                                             ##STR3##                                                                     ______________________________________                                    

The more preferred polysiloxane is the poly(organosiloxane) of formula Iabove. In the preferred embodiment A is acryloxy or methacryloxy andmore preferably methacryloxy.

R is preferably an alkylene radical. Therefore, preferably R ismethylene, propylene, butylene, pentamethylene, hexamethylene,octamethylene, dodecylmethylene, hexadecylmethylene andoctadecylmethylene. However, R can also be an arylene radical such asphenylene or biphenylene. More preferably R is an alkylene radicalhaving 1,3 or 4 carbon atoms. Most preferably R is an alkylene radicalhaving from about 3 to 4 carbon atoms, e.g., butylene.

Preferably R¹, R², R³ and R⁴ are alkyl radicals having from 1 to 12carbon atoms, e.g., methyl, ethyl, propyl, butyl, octyl, dodecyl and thelike; cycloalkyl radicals, e.g., cyclopentyl, cyclohexyl, cycloheptyland the like; mononuclear and binuclear aryl radicals, e.g., phenyl,naphthyl and the like; aralkyl radicals, e.g., benzyl, phenylethyl,phenylpropyl, phenylbutyl and the like; alkaryl radicals, e.g., tolyl,xylyl, ethylphenyl and the like; haloaryl radicals such as chlorophenyl,tetrachlorophenyl, difluorophenyl and the like; halo substituted loweralkyl radicals having up to about four alkyl carbon atoms such asfluoromethyl and fluoropropyl. More preferably R¹, R², R³ and R⁴ aremethyl radicals and phenyl radicals, most preferably each substituent ismethyl.

Preferably R⁵ and R⁶ are selected from the group consisting of hydrogen,hydrocarbon containing from 1 to about 6 carbon atoms and a carboxylicacid group. More preferably R⁵ and R⁶ are selected from the groupconsisting of hydrogen and methyl.

Preferably R⁷ is a hydrocarbon group containing from 1 to about 6 carbonatoms and most preferably is methyl.

Preferably R⁸ and R⁹ are each selected from the group consisting ofhydrogen and hydrocarbon containing from 1 to about 4 carbon atoms. Mostpreferably R⁸ and R⁹ are each selected from the group consisting ofhydrogen and methyl.

The polyparaffinsiloxane monomers employed in this invention areprepared according to the method disclosed in U.S. Pat. No. 4,208,506,granted June 17, 1980.

The method of preparation of the poly(organosiloxane) monomer isdisclosed in U.S. Pat. No. 4,153,641, granted May 8, 1979.

The second component of the polymer of this invention is a strengthmember which improves the modulus property of the polysiloxane with aminimum reduction of the oxygen permeability property. The polymer ofthis invention has a flexural modulus of at least a 1,000 Kg/cm². Forconvenience the function can be referred to as an oxygen permeablemodulus modifier (or OPMM). OPMM of this invention is a cycloalkylacrylate or methacrylate and is of the formula ##STR4## wherein E iseither hydrogen or methyl

D is branched or normal alkyl having 3 to 6 carbon atoms, preferably 3to 4 carbon atoms

Z is either hydrogen or methyl and

n is an integer from 3 to 8 and preferably from 4 to 6.

Illustrative of the foregoing OPMM are the following: Menthylmethacrylate, menthyl acrylate, tertiary-butylcyclohexyl methacrylate,isopropylcyclopentylacrylate, tertiarypentylcycloheptylmethacrylate,tertiarybutylcyclohexylacrylate, isohexylcyclopentylacrylate andmethylisopentyl cyclooctylacrylate.

OPMM is present in an amount from 90 to 30 parts by weight per 10 to 70parts by weight of the above described polysiloxane monomers. In eachevent, the total parts of OPMM and polysiloxane present are 100 parts.More preferably OPMM is present in the amount of 70 to 40 parts, morepreferably yet OPMM is 55 parts.

The relative hardness (or softness) of the contact lenses, i.e., polymerof this invention can be varied by the amount of modulus modifieremployed. Further small changes in the relative hardness can be obtainedby decreasing or increasing the molecular weight of the monomericpolysiloxane endcapped with the activated, unsaturated groups. As theratio of siloxane units to endcap units increases, the softness of thematerial increases. Conversely, as this ratio decreases, the rigidityand hardness of the material increases.

The third component of the polymeric composition of this invention isthe tear film stabilizer hydrophilic monomer. The stabilizer is presentin an amount of 2 to 20 parts by weight for each 100 parts ofpolysiloxane and modulus modifier. More preferably, the stabilizer willbe employed in the amount of 3 to 12 parts. Most preferably thestabilizer will be present in an amount of 5 to 9 parts.

While not wishing to be bound by any particular rationale, it appearsthat contact lenses on introduction to the eye tend to alter the layersof material over or on the cornea and inhibit the formation of a filmover the contact lenses. It is believed that the incorporation of a tearfilm stabilizer into the polymer matrix permanently reduces or avoidsthe film formation problem and allows tear fluids to coat the lenses.The prior art has sought to achieve this effect, in part, by the use ofhydrophilic coatings on the lenses but the coatings are subject toremoval on repeated handling of the lenses.

The tear film stabilizer is selected from the group consisting ofhydroxypropyl acrylate, hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate and mixtures thereof. Theforegoing propyl compounds may be in either the normal propyl or theisopropyl configurations. Of the foregoing stabilizers, hydroxyethylmethacrylate is the most preferred.

Optionally, the above three-component polymer system can contain fromzero to 20 parts by weight, based on weight of polysiloxane and OPMM, ofan auxiliary modifier. These auxiliary modifiers are reactive with thethree components of this invention. Minor but often desirable changes ofphysical properties, e.g., tear strength and tensile strength, areobtained by the use of auxiliary modifiers.

Useful auxiliary modifiers include, but are not limited to,tertiary-butyl acrylate, polyethylene glycol acrylate, polyethyleneglycol diacrylate, polyethylene glycol methacrylate, neopentyl glycoldiacrylate, neopentyl glycol dimethacrylate, polyethylene glycoldimethacrylate, divinyl benzene, polyvinyl alkyl benzenes, especiallydivinyl alkyl benzenes, e.g., divinyl toluene,1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane and mixturesthereof. The foregoing polyethylene glycols will contain from 2 to 9repeating ethylene glycol units.

The polysiloxanes α,ω terminally bonded through a divalent hydrocarbongroup to an activated unsaturated group, i.e., the monomers herein, aregenerally clear, colorless liquids whose viscosity depends on the valueof m or n. These monomers can be readily cured to cast shapes byconventional methods such as free radical initiators. Illustrative offree radical initiators which can be employed are bis(isopropyl) peroxydicarbonate, azobisisobutyronitrile, acetyl peroxide, benzoin methylether, lauroyl peroxide, decanoyl peroxide, benzoyl peroxide,diethoxyacetophenone, tertiarybutyl peroxypivalate and the like.

The process of lengthening the siloxane portion of the monomer isreferred to herein as siloxane ring insertion. The chain length of thepolysiloxane center unit of the monomers may be as high as 100.

The term polymerization is used to refer to the polymerization of thepolysiloxanes endcapped with polymerizable activated unsaturated groupswhich results in a crosslinked three-dimensional polymeric network.

The advantages of using the contact lenses, i.e., polymers of theinstant invention which are made from the monomers disclosed herein arenumerous. For example, the advantages of using activated vinyl terminalgroups to cure the siloxane material are (a) the high reactivity systemspermit rapid cure at or near room temperature if suitable initiators areused. (b) No fillers are needed to get useful physical strength as iscommon with most silicone resins in contact lenses. This is desirablesince the use of fillers requires that other possibly undesirablematerials be added to the composition in order to match the refractiveindex of the polymer to the filler.

Secondly, the contact lenses made from the polymer of the instantinvention are oxygen permeable. A critical oxygen tension and flux undera lens should be about 10 mmHg and 2 ml/(cm² hr.) respectively belowwhich corneal swelling occurs, Polse and Decker, InventigativeOphthalmology and Visual Science, vol. 18, p 188, 1979. In order to meetthese requirements the lens material must have adequate oxygenpermeability. When m in formula I and n in II above are at least about4, the chain of siloxane is long enough in the instant composition toexceed the oxygen requirements of the cornea. However, in specificsituations m and n may be as low as 0.

Additionally, these lenses are hydrolytically stable meaning that whenthe contact lenses are placed into an aqueous solution, e.g., on theeye, or during the disinfecting step, i.e., water plus heat, the lenseswill not change in chemical composition, i.e., hydrolyze.

The most preferred contact lens of the instant invention is afillerless, oxygen permeable, hydrolytically stable, biologically inert,transparent, hard, polymeric contact lens comprising apoly(organosiloxane) terminally bonded through a divalent hydrocarbongroup to a polymerized activated, unsaturated group. These mostpreferred contact lenses have an oxygen permeability of at least about10×10⁻¹¹ cm³ cm/(sec. cm² mmHg), are hydrolytically stable, biologicallyinert and transparent.

The polymers of this invention can be formed into contact lenses by thespincasting process as disclosed in U.S. Pat. Nos. 3,408,429 and3,496,254 and other conventional methods such as compression molding asdisclosed in U.S. Pat. Nos. 4,084,459 and 4,197,266.

These polymers can also be used in preparing medical surgical devices,e.g., heart valves, vessel substitutes, intrauterine devices, membranesand other films, dialyzer diaphragms, catheters, mouth guards, dentureliners and other such devices as disclosed in Shephard U.S. Pat. Nos.3,618,231 and 3,520,949. The instant polymers can be used to modifycollagen to make blood vessels, urinary bladders and other such devicesas disclosed in Kliment, U.S. Pat. No. 3,563,925. Also, these polymerscan be used to make catheters as disclosed in Shephard U.S. Pat. No.3,566,874. These polymers can be used as semipermeable sheets fordialysis, artifical dentures and all of such disclosures as set forth inStoy, U.S. Pat. No. 3,607,848. The instant polymers can be used inmaking breathable leather and other materials as disclosed in Shephard,U.S. Pat. No. 3,660,218. The polymers can be used in making printingplates and for other similar type uses as disclosed in Takaishi, U.S.Pat. No. 3,733,200.

The terms "shaped article for use in biomedical applications" or"biomedical device" mean the materials disclosed herein havephysiochemical properties rendering them suitable for prolonged contactwith living tissue, blood and the mucous membranes. These properties arerequired for biomedical shaped articles such as surgical implants, blooddialysis devices, blood vessels, artificial ureters, artificial breasttissue and membranes intended to come in contact with body fluid outsideof the body, e.g., membranes for kidney dialysis and heart/lung machinesand the like. It is known that blood, for example, is rapidly damaged incontact with artificial surfaces. The design of a synthetic surfacewhich is antithrombogenic and nonhemolytic to blood is necessary forprostheses and devices used with blood. The polymers and copolymers arecompatible with living tissue.

The polymers and copolymers disclosed herein can be boiled and/orautoclaved in water without being damaged whereby sterilization may beachieved. Thus, an article formed from the disclosed polymers andcopolymers may be used in surgery where an article compatible withliving tissue or with the mucous membranes may be used.

The following examples are illustrative only and should not be construedas limiting the invention. All parts and percents referred to herein areon a weight basis and all viscosities measured at 25° C. unlessotherwise specified.

EXAMPLE I

To a three-neck reaction vessel equipped with a mechanical stirrer andcalcium sulfate drying tube is charged 819.1 parts ofoctamethylcyclotetrasiloxane, 182.8 parts of1,3-bis(4-methacryloxybutyl) tetra methyl disiloxane and 2.5 parts oftrifluoromethane sulfonic acid. The reaction proceeds at roomtemperature. After a reaction time of three hours, the catalyst isneutralized with a 10 fold excess (13.9 parts) of sodium bicarbonate.Stirring is continued for about three hours to insure completeneutralization. The crude reaction product is filtered through a columnpacked with Celite® brand diatomaceous earth and activated alumina(Alcoa F20 grade). The resulting filtrate is freed of volatiles bypassing it over a thin film evaporator operating at 110° C. temperatureand 0.25 torr pressure. The final prepolymer product has a viscosity of0.28±0.05 stokes and approximately 25 dimethylsiloxy repeating units.

EXAMPLE II

Example I is repeated except that 890.4 parts ofoctamethylcyclotetrasiloxane and 100.6 parts of1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane are used. Theresulting prepolymer resin has approximately 50 dimethylsiloxy repeatingunits.

EXAMPLE III

A siloxane monomer similar to that of Example II, except that the numberof dimethylsiloxy repeating units is 15, is prepared.

EXAMPLE IV

A casting solution is prepared by mixing together 60 parts of the siloxymonomer of Example I, 40 parts of tertiarybutylcyclohexylmethacrylate, 9parts of hydroxyethylmethacrylate and 3 parts of tertiary-butylperoctoate catalyst. The solution is cast between glass plates. Thecasting is maintained at 60° C. for one-half hour and then 100° C. forapproximately one hour to obtain a film (approximately 30 mm thick)which is removed from between the plates and then devolatilized for 15minutes at 80° C. Physical test values otained on the film are asfollows:

    ______________________________________                                        Flexural Strength (ASTM D-790)                                                                      51 Kg/cm.sup.2                                          Flexural Modulus (ASTM D-790)                                                                       1,112 Kg/cm.sup.2                                       Impact Strength (ASTM D-256)                                                                        74.22 J/m                                               (Notched Izod)        (Joules/meter)                                          Deflection (ASTM D-790)                                                                             14.9 mm                                                 Oxygen Permeability - Approx.                                                                       11.6 × PHEMA                                      ______________________________________                                    

A typical oxygen permeability value for PHEMA(polyhydroxyethylmethacrylate) hydrogel is 8.0×10⁻¹¹ cm³ /(sec.cm²atm.). The oxygen permeability measurements were made using a flatpolarographic sensor. The method used was basically that described byRefojo et al (Refojo, M., Holly, F., and Leong, F-L., Contact andIntraocular Lens Medical Journal, Vol. 3, issue 4, p 27 (1977). Thevalues have been corrected for sample thickness.

EXAMPLE V

Following the procedure of Examples I and IV, additional polymers areprepared and tested. These results are summarized in Table I below. Thepolymers are clear and suitable for optical use.

                  TABLE I                                                         ______________________________________                                        Composition            A       B                                              ______________________________________                                        Monomer of Example I   50      40                                             Tertiary butylcyclohexylmethacrylate                                                                 50      60                                             Hydroxyethylmethacrylate                                                                             9       9                                              Flexural Strength, Kg/cm.sup.2                                                                       156     247                                            Flexural Modulus, Kg/cm.sup.2                                                                        4,103   6,820                                          Barcol Hardness        27      42                                             Impact Strength (Izod) J/m                                                                           93.93   60.88                                          Deflection, (ASTM D-790) mm                                                                          10      9.1                                            Oxygen Permeability × PHEMA                                                                    7.2     3.4                                            ______________________________________                                    

EXAMPLE VI

A casting solution is prepared by mixing together 40 parts of the siloxymonomer of Example II, 60 parts of isopentylcyclooctylmethacrylate, 6parts of hydroxypropylacrylate and 2 parts of diethoxyacetophenone. Themixed, degassed solution is placed in a suitable contact lensspincasting mold. It is spincast with ultraviolet radiation for one-halfhour to obtain the desired lens. The lens is optically clear, oxygenpermeable, hard and strong.

EXAMPLE VII

Casting solutions are prepared wherein the siloxy monomer hasapproximately 15 dimethylsiloxy repeating units (same as Example III).In each case, the OPMM is tertiarybutylcyclohexylmethacrylate and thetear film modifier is hydroxyethylmethacrylate. Using the procedure ofExample IV, films are prepared and tested. The compositions and testresults are summarized in Table II below.

                  TABLE II                                                        ______________________________________                                        Composition       A      B      C    D    E                                   ______________________________________                                        Siloxane, Parts   63     55     58   60   74                                  OPMM, Parts       37     45     42   40   26                                  Tear Film Modifier, Parts                                                                       5      5      5    5    5                                   Flexural Strength, Kg/cm.sup.2                                                                  79     163    --   96   --                                  Flexural Modulus, Kg/cm.sup.2                                                                   1,782  4,699  --   2,643                                                                              --                                  Barcol Hardness   21     41     30   21   15                                  Impact Strength (Notched Izod                                                 ASTM D-256) J/m   57.67  79.03  --   64.61                                                                              --                                  Deflection, (ASTM D-790) mm                                                                     12.1   9.7    --   11.4 --                                  Oxygen Permeability × PHEMA                                                               8.9    5.8    5.8  4.1  9.9                                 ______________________________________                                    

EXAMPLE VIII

A copolymer is prepared by making a solution of 20 parts of theprepolymer of Example I, 40 parts of the prepolymer of Example II, 40parts of menthylacrylate, 6 parts of hydroxypropylmethacrylate, 4 partsof 1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane and 3 parts ofbenzoyl peroxide and then cured to obtain a clear, hard polymer foroptical purposes.

EXAMPLE IX

To a round bottom polymerization flask, at room temperature, is charged85.5 g of 1,1,3,3-tetramethyl-1,3 disila-2-oxacyclopentane, 3.1 g of1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane and 1.3 ml oftrifluoromethane sulfonic acid. The reaction is mildly exothermic. Theflask's contents are agitated on a shaker overnight. The reactants areneutralized with an excess of sodium bicarbonate, diluted with hexaneand filtered to remove the carbonate. The hexane diluted product is thenwashed three times with water and dried over anhydrous magnesiumsulfate. The hexane is removed at reduced pressure. By gel permeabilitychromatography, it is determined that the polyparaffinsiloxane has 75ethylene disiloxane repeating units.

EXAMPLE X

A solution containing 70 parts of tertiarybutyl cyclohexylmethacrylate,30 parts of the prepolymer resin of Example VIII, 2 parts ofhydroxyethylmethacrylate, 2 parts of tertiary-butyl peroctoate and 2parts of sec. butyl peroctoate is cast into film following the procedureof Example IV.

EXAMPLE XI

Example IX is repeated except that the ratio ofdisilatetramethyloxacyclopentane to bis-(methacryloxybutyl) tetramethyldisiloxane is 20:1. The resulting polyparaffinsiloxane monomer has 56ethylene disiloxane repeating units.

EXAMPLE XII

A solution containing 60 parts of menthyl acrylate, 40 parts of theprepolymer resin of Example XI, 2 parts of hydroxypropyl acrylate, 1part of tertiary-butyl peroctoate and 2 parts of sec. butyl peroctoateis cast into film following the procedure of Example IV.

The preceding examples and methods have been described in the foregoingspecification for the purpose of illustration and not limitation. Othermodifications and ramifications will naturally suggest themselves tothose skilled in the art based on the disclosure. These are intended tobe comprehended as within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A shaped article suitable for use in biomedical applications being a polymer formed by polymerizing (a) one or more polysiloxane monomers α,ω terminally bonded through divalent hydrocarbon groups to an activated unsaturated group with (b) a cycloalkyl modulus modifier and (c) a tear film stabilizer to form a crosslinked three-dimensional polymeric network.
 2. The article of claim 1 wherein the modulus modifier is present in an amount from 90 to 30 parts per 10 to 70 parts of polysiloxane monomers and the sum of parts equals
 100. 3. The article according to claim 2 wherein from 70 to 40 parts of modulus modifier are present.
 4. The article according to claim 3 wherein 55 parts of modulus modifier are present.
 5. The article according to claim 1 wherein the cycloalkyl modifier is of the formula ##STR5## wherein: D is branched or normal alkyl of 3 to 6 carbon atomsE is H or CH₃ Z is H or CH₃ n is an integer from 3 to
 8. 6. The article according to claim 5 wherein D is a branched alkyl of 3 or 4 carbon atoms and n is an integer from 4 to
 6. 7. The article according to claim 6 wherein the modifier is tertiarybutylcyclohexyl methacrylate.
 8. The article according to claim 2 wherein 2 to 20 parts of tear film stabilizer are present per 100 parts of modulus modifier and polysiloxane monomer.
 9. The article according to claim 8 wherein 3 to 12 parts of tear film stabilizer are employed.
 10. The article according to claim 9 wherein from 5 to 9 parts of tear film stabilizer are present.
 11. The article according to claim 1 wherein the tear film stabilizer is selected from the group consisting of hydroxyethylmethacrylate, hydroxyethylacrylate, hydroxypropylmethacrylate, hydropropylacrylate and mixtures thereof.
 12. The article according to claim 11 wherein the tear film stabilizer is hydroxyethylmethacrylate.
 13. The article according to claim 1 wherein an auxiliary modifier selected from the group consisting of tertiary-butyl acrylate, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, 1,3-bis(4-methacryloxybutyl) tetramethyl disiloxane, polyethylene glycol acrylate, polyethylene glycol diacrylate, divinyl benzene, divinyl alkyl benzene mixtures thereof is present in an amount of up to 20 parts by weight per 100 parts of tertiary-butyl styrene and polysiloxane.
 14. The article according to claim 13 wherein from zero to 10 parts auxiliary modifier are present.
 15. The article according to claim 1 wherein the polysiloxane is a poly(organosiloxane) of the formula ##STR6## wherein A is an activated unsaturated group, R is a divalent hydrocarbon radical having from 1 to about 22 carbon atoms, R¹, R², R³ and R⁴ can be the same or different and each is a monovalent hydrocarbon radical each having from 1 to about 12 carbon atoms and m is an integer from 0 to
 100. 16. The article according to claim 15 wherein A is methacryloxy, R is a divalent hydrocarbon radical having from 1 to about 22 carbon atoms, R¹, R₂, R³ and R⁴ can be the same or different and are selected from the group consisting of monovalent hydrocarbon radical or a halogen substituted monovalent hydrocarbon radical each having from 1 to 12 carbon atoms and m is an integer from 0 to
 50. 17. The article according to claim 16 wherein R is an alkylene radical and R¹, R², R³ and R⁴ are each analkyl radical having from 1 to 10 carbon atoms.
 18. The article according to claim 17 wherein m is a number from 0 to about
 25. 19. The article according to claim 1 wherein the polysiloxane is a polyparaffinsiloxane of the formula ##STR7## where A is an activated unsaturated group; R is a divalent hydrocarbon radical having from 1 to about 22 carbon atoms; R¹, R², R³ and R⁴ are ach independently selected from the group consisting of a monovalent hydrocarbon radical having from 1 to about 12 carbon atoms and a halogen substituted monovalent hydrocarbon radical having from 1 to about 12 carbon atoms and a halogen substituted monovalent hydrocarbon radical having from 1 to about 12 carbon atoms; R⁵ and R⁶ can be the same or different and are selected from the group consisting of hydrogen, a hydrocarbon radical containing from 1 to about 12 carbon atoms, a carboxylic acid group, a carboxylic acid ester group represented by the formula --C(O)OR⁷ wherein R⁷ is selected from the group consisting of a hydrocarbon group containing from 1 to 12 carbon atoms and a carboxylic acid amide represented by the formula --C(O)NR⁸ R⁹ wherein R⁸ and R⁹ can be the same or different and each is selected from the group consisting of hydrogen and a hydrocarbon group containing from 1 to about 12 carbon atoms; x is 2 or greater and n is an integer of 1 to about
 100. 20. The article according to claim 19 wherein R is an alkylene radical, R¹, R², R³ and R⁴ are each an alkyl radical having from 1 to 10 carbon atoms and R⁵ and R⁶ are each hydrogen or methyl and n is an integer from 1 to
 50. 21. The article according to claim 20 wherein n is a number from 1 to about 25 and x is an integer from 2 to
 10. 22. The article according to claim 21 wherein x is 2 or
 3. 23. The article according to claim 1 has a flexural modulus of at least 1,000 Kg/cm².
 24. Wherein the article according to claim 1 is a gas permeable hard contact lens. 